Bug 3107 - Mistake in config can result in fork bomb
Summary: Mistake in config can result in fork bomb
Status: CLOSED DUPLICATE of bug 3057
Alias: None
Product: Portable OpenSSH
Classification: Unclassified
Component: ssh (show other bugs)
Version: 8.1p1
Hardware: Other Linux
: P5 enhancement
Assignee: Assigned to nobody
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2019-12-21 21:25 AEDT by petoju
Modified: 2021-04-23 15:03 AEST (History)
0 users

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ssh_config causing fork bomb (72 bytes, application/octet-stream)
2019-12-21 21:25 AEDT, petoju 		no flags Details
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Description petoju 2019-12-21 21:25:36 AEDT 
Created attachment 3343 [details]
ssh_config causing fork bomb

When writing ssh_config, an innocuous mistake in ssh_config leads to a fork bomb.
One example is this config, use it when connecting to any host:

Host proxy
	Hostname doesnotmatter.example.com
Host *
	ProxyJump proxy

OpenSSH client tries to connect to the proxy first. To connect to the proxy, it has to connect to the very same proxy. It could be more complicated, but the issue is in the cycle.

Why is it annoying: one can effectively kill own system like this by mistake. No warning is provided.

What could OpenSSH do about it: warn that there is a cycle, recommend excluding "proxy" from ProxyJump and bail out.
Comment 1 petoju 2019-12-21 21:28:33 AEDT 

*** This bug has been marked as a duplicate of bug 3057 ***
Comment 2 Damien Miller 2021-04-23 15:03:58 AEST 
closing resolved bugs as of 8.6p1 release